drm: nova-drm: add initial driver skeleton

Add the initial nova-drm driver skeleton.

nova-drm is connected to nova-core through the auxiliary bus and
implements the DRM parts of the nova driver stack.

For now, it implements the fundamental DRM abstractions, i.e. creates a
DRM device and registers it, exposing a three sample IOCTLs.

  DRM_IOCTL_NOVA_GETPARAM
    - provides the PCI bar size from the bar that maps the GPUs VRAM
      from nova-core

  DRM_IOCTL_NOVA_GEM_CREATE
    - creates a new dummy DRM GEM object and returns a handle

  DRM_IOCTL_NOVA_GEM_INFO
    - provides metadata for the DRM GEM object behind a given handle

I implemented a small userspace test suite [1] that utilizes this
interface.

Link: https://gitlab.freedesktop.org/dakr/drm-test [1]
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Acked-by: Dave Airlie <airlied@redhat.com>
Link: https://lore.kernel.org/r/20250424160452.8070-3-dakr@kernel.org
[ Kconfig: depend on DRM=y rather than just DRM. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Author: Danilo Krummrich

MAINTAINERS

@@ -7594,6 +7594,18 @@ T:	git https://gitlab.freedesktop.org/drm/nova.git nova-next
 F:	Documentation/gpu/nova/
 F:	drivers/gpu/nova-core/
 
+DRM DRIVER FOR NVIDIA GPUS [RUST]
+M:	Danilo Krummrich <dakr@kernel.org>
+L:	nouveau@lists.freedesktop.org
+S:	Supported
+Q:	https://patchwork.freedesktop.org/project/nouveau/
+B:	https://gitlab.freedesktop.org/drm/nova/-/issues
+C:	irc://irc.oftc.net/nouveau
+T:	git https://gitlab.freedesktop.org/drm/nova.git nova-next
+F:	Documentation/gpu/nova/
+F:	drivers/gpu/drm/nova/
+F:	include/uapi/drm/nova_drm.h
+
 DRM DRIVER FOR OLIMEX LCD-OLINUXINO PANELS
 M:	Stefan Mavrodiev <stefan@olimex.com>
 S:	Maintained

drivers/gpu/drm/Kconfig

@@ -343,6 +343,8 @@ source "drivers/gpu/drm/amd/amdgpu/Kconfig"
 
 source "drivers/gpu/drm/nouveau/Kconfig"
 
+source "drivers/gpu/drm/nova/Kconfig"
+
 source "drivers/gpu/drm/i915/Kconfig"
 
 source "drivers/gpu/drm/xe/Kconfig"

drivers/gpu/drm/Makefile

@@ -176,6 +176,7 @@ obj-$(CONFIG_DRM_VMWGFX)+= vmwgfx/
 obj-$(CONFIG_DRM_VGEM)	+= vgem/
 obj-$(CONFIG_DRM_VKMS)	+= vkms/
 obj-$(CONFIG_DRM_NOUVEAU) +=nouveau/
+obj-$(CONFIG_DRM_NOVA) += nova/
 obj-$(CONFIG_DRM_EXYNOS) +=exynos/
 obj-$(CONFIG_DRM_ROCKCHIP) +=rockchip/
 obj-$(CONFIG_DRM_GMA500) += gma500/

drivers/gpu/drm/nova/Kconfig

@@ -0,0 +1,14 @@
+config DRM_NOVA
+	tristate "Nova DRM driver"
+	depends on AUXILIARY_BUS
+	depends on DRM=y
+	depends on PCI
+	depends on RUST
+	default n
+	help
+	  Choose this if you want to build the Nova DRM driver for Nvidia
+	  GSP-based GPUs.
+
+	  This driver is work in progress and may not be functional.
+
+	  If M is selected, the module will be called nova.

drivers/gpu/drm/nova/Makefile

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_DRM_NOVA) += nova.o

drivers/gpu/drm/nova/driver.rs

@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use kernel::{auxiliary, c_str, device::Core, drm, drm::gem, drm::ioctl, prelude::*, types::ARef};
+
+use crate::file::File;
+use crate::gem::NovaObject;
+
+pub(crate) struct NovaDriver {
+    #[expect(unused)]
+    drm: ARef<drm::Device<Self>>,
+}
+
+/// Convienence type alias for the DRM device type for this driver
+pub(crate) type NovaDevice = drm::Device<NovaDriver>;
+
+#[pin_data]
+pub(crate) struct NovaData {
+    pub(crate) adev: ARef<auxiliary::Device>,
+}
+
+const INFO: drm::DriverInfo = drm::DriverInfo {
+    major: 0,
+    minor: 0,
+    patchlevel: 0,
+    name: c_str!("nova"),
+    desc: c_str!("Nvidia Graphics"),
+};
+
+const NOVA_CORE_MODULE_NAME: &CStr = c_str!("NovaCore");
+const AUXILIARY_NAME: &CStr = c_str!("nova-drm");
+
+kernel::auxiliary_device_table!(
+    AUX_TABLE,
+    MODULE_AUX_TABLE,
+    <NovaDriver as auxiliary::Driver>::IdInfo,
+    [(
+        auxiliary::DeviceId::new(NOVA_CORE_MODULE_NAME, AUXILIARY_NAME),
+        ()
+    )]
+);
+
+impl auxiliary::Driver for NovaDriver {
+    type IdInfo = ();
+    const ID_TABLE: auxiliary::IdTable<Self::IdInfo> = &AUX_TABLE;
+
+    fn probe(adev: &auxiliary::Device<Core>, _info: &Self::IdInfo) -> Result<Pin<KBox<Self>>> {
+        let data = try_pin_init!(NovaData { adev: adev.into() });
+
+        let drm = drm::Device::<Self>::new(adev.as_ref(), data)?;
+        drm::Registration::new_foreign_owned(&drm, adev.as_ref(), 0)?;
+
+        Ok(KBox::new(Self { drm }, GFP_KERNEL)?.into())
+    }
+}
+
+#[vtable]
+impl drm::Driver for NovaDriver {
+    type Data = NovaData;
+    type File = File;
+    type Object = gem::Object<NovaObject>;
+
+    const INFO: drm::DriverInfo = INFO;
+
+    kernel::declare_drm_ioctls! {
+        (NOVA_GETPARAM, drm_nova_getparam, ioctl::RENDER_ALLOW, File::get_param),
+        (NOVA_GEM_CREATE, drm_nova_gem_create, ioctl::AUTH | ioctl::RENDER_ALLOW, File::gem_create),
+        (NOVA_GEM_INFO, drm_nova_gem_info, ioctl::AUTH | ioctl::RENDER_ALLOW, File::gem_info),
+    }
+}

drivers/gpu/drm/nova/file.rs

@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use crate::driver::{NovaDevice, NovaDriver};
+use crate::gem::NovaObject;
+use crate::uapi::{GemCreate, GemInfo, Getparam};
+use kernel::{
+    alloc::flags::*,
+    drm::{self, gem::BaseObject},
+    pci,
+    prelude::*,
+    types::Opaque,
+    uapi,
+};
+
+pub(crate) struct File;
+
+impl drm::file::DriverFile for File {
+    type Driver = NovaDriver;
+
+    fn open(_dev: &NovaDevice) -> Result<Pin<KBox<Self>>> {
+        Ok(KBox::new(Self, GFP_KERNEL)?.into())
+    }
+}
+
+impl File {
+    /// IOCTL: get_param: Query GPU / driver metadata.
+    pub(crate) fn get_param(
+        dev: &NovaDevice,
+        getparam: &Opaque<uapi::drm_nova_getparam>,
+        _file: &drm::File<File>,
+    ) -> Result<u32> {
+        let adev = &dev.adev;
+        let parent = adev.parent().ok_or(ENOENT)?;
+        let pdev: &pci::Device = parent.try_into()?;
+        let getparam: &Getparam = getparam.into();
+
+        let value = match getparam.param() as u32 {
+            uapi::NOVA_GETPARAM_VRAM_BAR_SIZE => pdev.resource_len(1)?,
+            _ => return Err(EINVAL),
+        };
+
+        getparam.set_value(value);
+
+        Ok(0)
+    }
+
+    /// IOCTL: gem_create: Create a new DRM GEM object.
+    pub(crate) fn gem_create(
+        dev: &NovaDevice,
+        req: &Opaque<uapi::drm_nova_gem_create>,
+        file: &drm::File<File>,
+    ) -> Result<u32> {
+        let req: &GemCreate = req.into();
+        let obj = NovaObject::new(dev, req.size().try_into()?)?;
+
+        req.set_handle(obj.create_handle(file)?);
+
+        Ok(0)
+    }
+
+    /// IOCTL: gem_info: Query GEM metadata.
+    pub(crate) fn gem_info(
+        _dev: &NovaDevice,
+        req: &Opaque<uapi::drm_nova_gem_info>,
+        file: &drm::File<File>,
+    ) -> Result<u32> {
+        let req: &GemInfo = req.into();
+        let bo = NovaObject::lookup_handle(file, req.handle())?;
+
+        req.set_size(bo.size().try_into()?);
+
+        Ok(0)
+    }
+}

drivers/gpu/drm/nova/gem.rs

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use kernel::{
+    drm,
+    drm::{gem, gem::BaseObject},
+    prelude::*,
+    types::ARef,
+};
+
+use crate::{
+    driver::{NovaDevice, NovaDriver},
+    file::File,
+};
+
+/// GEM Object inner driver data
+#[pin_data]
+pub(crate) struct NovaObject {}
+
+impl gem::BaseDriverObject<gem::Object<NovaObject>> for NovaObject {
+    fn new(_dev: &NovaDevice, _size: usize) -> impl PinInit<Self, Error> {
+        try_pin_init!(NovaObject {})
+    }
+}
+
+impl gem::DriverObject for NovaObject {
+    type Driver = NovaDriver;
+}
+
+impl NovaObject {
+    /// Create a new DRM GEM object.
+    pub(crate) fn new(dev: &NovaDevice, size: usize) -> Result<ARef<gem::Object<Self>>> {
+        let aligned_size = size.next_multiple_of(1 << 12);
+
+        if size == 0 || size > aligned_size {
+            return Err(EINVAL);
+        }
+
+        gem::Object::new(dev, aligned_size)
+    }
+
+    /// Look up a GEM object handle for a `File` and return an `ObjectRef` for it.
+    #[inline]
+    pub(crate) fn lookup_handle(
+        file: &drm::File<File>,
+        handle: u32,
+    ) -> Result<ARef<gem::Object<Self>>> {
+        gem::Object::lookup_handle(file, handle)
+    }
+}

drivers/gpu/drm/nova/nova.rs

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Nova DRM Driver
+
+mod driver;
+mod file;
+mod gem;
+mod uapi;
+
+use crate::driver::NovaDriver;
+
+kernel::module_auxiliary_driver! {
+    type: NovaDriver,
+    name: "Nova",
+    author: "Danilo Krummrich",
+    description: "Nova GPU driver",
+    license: "GPL v2",
+}

drivers/gpu/drm/nova/uapi.rs

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use kernel::uapi;
+
+// TODO Work out some common infrastructure to avoid boilerplate code for uAPI abstractions.
+
+macro_rules! define_uapi_abstraction {
+    ($name:ident <= $inner:ty) => {
+        #[repr(transparent)]
+        pub struct $name(::kernel::types::Opaque<$inner>);
+
+        impl ::core::convert::From<&::kernel::types::Opaque<$inner>> for &$name {
+            fn from(value: &::kernel::types::Opaque<$inner>) -> Self {
+                // SAFETY: `Self` is a transparent wrapper of `$inner`.
+                unsafe { ::core::mem::transmute(value) }
+            }
+        }
+    };
+}
+
+define_uapi_abstraction!(Getparam <= uapi::drm_nova_getparam);
+
+impl Getparam {
+    pub fn param(&self) -> u64 {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_getparam`.
+        unsafe { (*self.0.get()).param }
+    }
+
+    pub fn set_value(&self, v: u64) {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_getparam`.
+        unsafe { (*self.0.get()).value = v };
+    }
+}
+
+define_uapi_abstraction!(GemCreate <= uapi::drm_nova_gem_create);
+
+impl GemCreate {
+    pub fn size(&self) -> u64 {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_gem_create`.
+        unsafe { (*self.0.get()).size }
+    }
+
+    pub fn set_handle(&self, handle: u32) {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_gem_create`.
+        unsafe { (*self.0.get()).handle = handle };
+    }
+}
+
+define_uapi_abstraction!(GemInfo <= uapi::drm_nova_gem_info);
+
+impl GemInfo {
+    pub fn handle(&self) -> u32 {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_gem_info`.
+        unsafe { (*self.0.get()).handle }
+    }
+
+    pub fn set_size(&self, size: u64) {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_gem_info`.
+        unsafe { (*self.0.get()).size = size };
+    }
+}